Ductwork forming machine

ABSTRACT

There is disclosed herein a machine with control means for automatically carrying out a plurality of ductwork forming operations on a substantially flat blank of precut sheet metal. The blank is clamped down on a horizontal bed by an elongated clamping member. A generally X-shaped press forming device or cross break creases the metal to form a slightly frustopyramidal crown in that portion of the metal which projects on one side of the clamping member, and individual dies punch offset strap locks in the metal at one lateral edge of the blank adjacent to the crown. A pivotable table folds the metal which projects on the opposite side of the clamping member upwardly at right angles to the crowned portion whereupon die members form right angle bends in the side edges of the upwardly bent portion of the metal and then move inwardly to form inwardly folded cleat connector flanges. The die members then retract and the table returns to a horizontal position.

United States Patent 11 1 Hugert 1 51 Apr. 10, 1973 [54] DUCTWORK FORMING MACHINE [75] Inventor: George J. Hugert, Medina, Ohio [73] Assignee: Hugert Manufacturing Company,

Medina, Ohio 1 22 Filed: Dec. 2; 1971 21 App1.No.: 204,271

[52] US. Cl. ..72/306, 72/319, 113/54 [51] Int. Cl. ..B2ld 39/02 [58] Field of Search ..72/306, 319, 320,

[56] References Cited UNITED STATES PATENTS 3,009,179 1 1/196] Schramm ..72/306 3,149,376 9/1964 Lee ..72/306 3,191,419 6/1965 Rippe ..72/306 3,422,525 1/1969 Jeppsson ..1 13/54 3 258,948 7/ l 966 Carlson, Sr ..72/465 I Primary Examiner-Richard J. Herbst Attorney-J. H. Slough ABSTRACT There is disclosed herein a machine with control means for automatically carrying out a plurality of ductwork forming operations on a substantially flat blank of precut sheet metal. The blank is clamped down on a horizontal bed by an elongated clamping member. A generally X-shaped press forming device or cross break creases the metal to form a slightly frustopyramidal crown in that portion of the metal which projects on one side of the clamping member, and individual dies punch ofiset strap locks in the metal at one lateral edge of the blank adjacent to the crown. A pivotable table folds the metal which projects on the opposite side of the clamping member upwardly at right angles to the crowned portion whereupon die members form right angle bends in the side edges of the upwardly bent portion of the metal and then move inwardly to form inwardly folded cleat connector flanges. The die members then retract and the table returns to a horizontal position.

40 Claims, 23 Drawing Figures PATENTED APR 1 0 I975 SHEET 2 0F 7 PATENT APRIOISYS EU V 8,726,120

sum 3 or 7 PATENTED AFR 1 0 975 SHEET 5 [1F 7 DUCTWORK FORMING MACHINE This invention relates to the manufacture of sheet metal ductwork for air circulation purposes and particularly to a machine for automatically carrying out a plurality of forming operations on a substantially flat blank of precut sheet metal.

Present ductwork manufacturing procedures comprise performing a plurality of separate operations wherein creases, bends, folds, etc. are formed in a piece of sheet metal by manual manipulation of the sheet with respect to various tools and apparatuses. A complete unit or section of ductwork of the type herein referred to comprises two modular portions which are substantially L-shaped in cross section and, when fitted together in a complementary manner, form a unit of ductwork which is substantially rectangular in cross section. The present invention is directed to a machine for automatically carrying out several different forming operations on a precut sheet metal bland whereby a modular portion is formed.

The general object of the invention is to provide a machine which carries out a plurality of forming operations on a sheet metal blank more'efficiently than present methods.

Another object of the invention is to provide a ductwork forming machine which is particularly adapted for forming substantially flat sheet metal blanks into I..- shaped modular portions for assembly into rectangular ductwork sections.

Still another object of the invention is to provide a machine as set forth above having unique means for forming a slightly frustopyramidal crown in one wall of the ductwork.

Yet another object of the invention is to provide a ductwork forming machine having the above features and characteristics including novel means for forming at least one outwardly folded cleat connector flange adapted to be disposed at one end of a completed ductwork section.

A further object of this invention is to provide means for folding a portion of the sheet metal blank at right angles to the remainder of the blank and means adjacent to the ends of the folded portion for engaging said ends and forming thereon outwardly folded cleat connector flanges.

A still further object of the invention is to provide a ductwork forming machine as set forth above including means for retracting said means engaging the ends of the folded portion whereby to free the same for removal from the machine.

Another object of this invention is to provide a ductwork forming machine having in addition to the above features and characteristics, control means for automatically cycling the machine through a plurality of operations whereby to automatically form modular portions of ductwork.

Other objects and advantages of the invention will be readily understood from the following description of the invention as disclosed in the accompanying drawings, in which said drawings:

FIG. 1 is a front elevation of the ductwork forming machine of this invention;

FIG. 2 is a top plan view of the machine;

FIG. 3 is an end elevation of the machine as seen from the left side of FIG. 1;

FIG. 4 is a fragmentary front elevational view showing a detail of a pivoted table portion of the machine in its upwardly pivoted position;

FIG. 5 is an enlarged section of a press forming device taken generally along the line 5-5 of FIG. 2;

FIG. 6 is a section taken along the line 6-6 of FIG.

FIG. 7 is a fragmentary top plan view of a portion of the press forming device of FIG. 5;

FIG. 8 is an elevation of the portion of the press forming device shown in FIG. 7;

FIG. 9 is an enlarged perspective view of an outer flange forming die member of the machine;

FIG. 10 is a section taken along the line 10--10 of FIG. 9;

FIG. 11 is an enlarged side elevation of a die adapted to punch offset strap locks in the sheet metal blank, the view being taken along the line 1 1-11 of FIG. 2;

FIGS. 12, 13 and 14 are enlarged fragmentary top plan views of outer and inner flange forming die members in successive operative positions for forming a cleat connector flange;

FIG. 15 is an enlarged sectional detail of the pivoted table of the machine;

FIG. 16 is an enlarged section taken generally along the line 16-46 of FIG. 4 showing a releasable stop mechanism;

FIG. 17 is a section taken along the line 17-17 of FIG. 16;

FIGS. 18 and 19 comprise electrical diagrams showing control means for the machine;

FIG. 20 is a perspective view showing one modular portion in full line and a second modular portion so connected to the first portion as to form a section or unit of ductwork;

FIG. 21 is an enlarged section showing the manner in which edges of two modular portions are fastened to form a section of ductwork;

FIG. 22 is an enlarged section showing the manner in which certain walls of adjacent sections of ductwork are fastened together; and

FIG. 23 is an enlarged section showing the manner in which certain other walls of adjacent sections of ductwork are fastened.

Referring now to the drawings in all of which like parts are designated by like reference numerals, the ductwork forming machine of this invention comprises a skeletal steel frame 1 constructed, for example, from welded rectangular steel tubing. At an intermediate level suitable for hand feeding by an operator said frame is provided with a flat, horizontal bed 2 having a tough, elastic pad 3 of rubber or similar material superimposed thereon. A press forming device, also referred to as a cross break or cross break device, generally indicated at 4, is disposed above the pad 3 within the volume of the frame adjacent to the front, work receiving side thereof, the same being the lowermost side in FIG. 2 and the right-hand side in FIG. 3. A flat, normally horizontal, pivoted table 5 is mounted to the front of the frame and projects forwardly therefrom coplanar with the upper surface of the pad 3 in its normal horizontal position (FIGS. 3 and 15). A vertically acting, elongated clamping bar 6 is adapted to move downwardly against the sheet metal blank whereby upward pivoting of the table 5 will bend the blank into an L-shape to provide two right angularly disposed walls 7 and 8 of a section of ductwork. The sheet metal blank is shown in broken or phantom line at B in FIG. 2, and it will be readily appreciated that one portion of the blank projects under the cross break 4 and becomes one wall of the duct, and another portion of the blank overlies the table and is bent upwardly about the elongated clamp 6 and becomes another wall of the duct. The cross break 4 presses downwardly against the wall 7 and forms a slightly frustopyramidal crown therein while a pair of small notching or piercing dies 9 and 10 form a pair of offset strap locks D in one end edge portion of said wall 7. The upwardly bent portion of the blank B which forms the wall 8 is meanwhile provided with outwardly turned cleat connector flanges F (FIG. 20) by means of outer and inner flange forming dies generally indicated at 11 and 12, respectively, in FIG. 1.

The frame 10 includes front and back, parallel, horizontal support members 13 and 14, respectively, between which are provided spaced, parallel fore and aft frame members 15 and 16 which provide guideways or tracks for adjustably mounting the cross break 4. It is desirable that said cross break have a fore and aft adjustment between the front and back of the machine whereby the same can be centered over that portion of the blank B which is to become the crowned wall 7. It also makes the cross break 4 adaptable for use in forming various size ductwork as will hereinlater become apparent.

The cross break 4 comprises a vertically acting cylinder 20 mounted between two vertical supports 21 (FIG. 3) which are, in turn, mounted upon a horizontal support plate 22. The lateral side edge portions of the support plate 22 project under the fore and aft frame members 15 and 16, and upwardly offset generally,Z- shaped brackets 23 overlap the upper surfaces of said fore and aft frame members whereby the cross break 4 is slidable between the front and rear of the machine. Such fore and aft adjustment of the cross break is effected by an elongated, threaded rod 24 which is pivoted freely in an upwardly projecting bearing 25 at the rear edge of the support plate 22 and is threadfitted within an upstanding bracket 26 carried on the upper surface of the back horizontal support member 14. The rearwardly projecting end of the rod 24 is provided with a crank 27 whereby the rod 24 can be rotated to adjust the cross break forwardly or rearwardly.

The cross break 4 further comprises a downwardly projecting columnar structure including a piston rod 30 best seen in FIG. 5. Said piston rod has a small, heavy rectangular connector plate 31 secured to the lower ends thereof by any suitable means such as a bolt 32. The connector plate 31 carries outwardly projecting, elongated blades 33 disposed in vertical planes at the four corners thereof, each blade having a lower creasing edge and a cutout 34 at its inner end in which a corner of the connector plate 31 loosely fits. Above the cutout 34, each blade 33 is provided with an axially vertical bearing 35. The connector plate 31 is welded or otherwise rigidly secured to the lower end of a rectangular outer housing 36 which projects upwardly a substantial distance above the blades 33. At a vertically intermediate portion, the outer housing 36 projects through and has secured thereto a circular plate 37 which projects over the upper ends of the bearings 35. The blades 33 are pivoted in a horizontal plane between the plates 31 and 37 by vertical bolts 38 which project through suitable aligned openings in said plates and through the bearings 35, there being sufficient play in said pivots to afford slight up and down pivotal movement at the outer ends of said blade.

At the upper end of the rectangular housing 36 there is provided a third plate 39 of rectangular shape to the four corners of which are connected turnbuckle expansion adjusters 40. Each adjuster 40 is provided at the inner and outer ends thereof with oppositely threaded rods 41 and 42, respectively, the inner rod 41 having a clevis 43 pivoted to one corner of the plate 39 by means of a pin 44, and the outer rod 42 having a clevis 45 pivoted to an upstanding bracket 46 adjacent to the outer end of the associated blade by means of a pin 47. It will be readily understood that by rotation of the adjusters 40, the relative pressure between the inner and outer end of each blade 33 can be adjusted as desired. Generally, it is preferred to have slightly greater pressure adjacent to the columnar structure and slightly less at the outer ends of the blades to attain the desired crowning effect.

The rectangular housing 36 is slidably disposed over a tubular rectangular inner housing 50 having a radially projecting flange 51 bolted to the horizontal support plate 22. The piston rod 30 projects slidably downwardly through the inner housing 50 whereby upon actuation of the cylinder and piston motor 20, the outer housing 36 and all of the blades 33 are brought downwardly to form a generally X-shaped crease in the sheet metal blank whereby a slightly frustopyramidal, outwardly projecting crown is formed therein. Crowning or cross breaking of a wall of sheet metal ductwork for the purpose of stiffening the wall and preventing its distortion and popping due to temperature changes is well known and it will be readily understood that the cross break of the present invention affords such crowning in a single stamping operation.

To assure that the X formed by the cross break 4 is at all times symmetrical, the pair of blades on either side of the cylinder and piston motor 20 are connected adjacent to their outer ends by a pair of links 52 and 53 pivoted on brackets 58 and 59, respectively, which said links converge inwardly toward the cylinder and piston motor 20 and are pivoted to each other at their inner ends by suitable pivot means such as nut and bolt assemblies 54 (FIG. 5). Elongated guide bars 55 are secured at their inner ends to the medial plates 37 of the outer housing 36 and project laterally at right angles to the fore and aft direction of movement of the cross break 4. The outer end portions of said guide bars are provided with elongated slots 56, the bolts 54 of each pair of links 52 and 53 projecting through the adjacent of said slots 56. Thus the bolts 54 can only move in a straight line whereby the blades 33 of each pair are always maintained symmetrically spread apart with respect to a center line through the guide bars 55.

The ends of the blades 33 disposed adjacent to the front of the machine are held by means of a pair of angle shaped, pivoted retainers 60, one of which is detailed in FIGS. 7 and 8. Each retainer comprises a bracket 61 having an upstanding wall 62 from which projects parallel horizontal, spaced ears or arms 63. Between the arms 63 there is pivotally mounted an angle member 64 having one leg 65 thereof overlapping the end of the adjacent blade 33 and having another leg 66 thereof disposed at a slight angle to and spaced from the upstanding wall 62. A strong coil spring 67 is compressively mounted between the upstanding wall 62 and the leg 66 whereby the leg 65 is strongly urged against the adjacent blade 33. Thus it will be seen that when the cross break 4 is adjusted in a rearward direction to accommodate a blank 13 of greater size, the forwardly disposed blades will be held at their ends in a location adjacent to the front of the machine and all of the blades will spread and angle symmetrically as the cylinder and piston motor is adjusted rearwardly. Forward adjustment of said cylinder and piston motor causes said legs to close while maintaining the aforesaid symmetry.

The pivoted table 5 and the clamping bar 6 work in conjunction with each other to form the primary, right angle bend of a modular portion M shown in FIG. 18. Referring now particularly to FIGS. 1, 4, and 5, the

table 5 is secured at right angles to a normally downwardly projecting plate 70 having laterally projecting journals 71 pivoted in bearings 72 carried by the frame 1. The normally rearwardly or backwardly facing surface of the plate 70 is provided with a pair of bearings 73, and directly in alignment with each bearing 73, the frame 1 is provided with a subframe 74 adapted for mounting a cylinder and piston motor 75. Each said cylinder and piston motoris pivoted at its rearward end to an L-shaped bracket 76 of said subframe by means of a pin 77, and each said cylinder and piston motor has a forwardly and upwardly directed piston rod 78, the forward end of which has a clevis 79 pivotally mounted to one of the bearings 73 by means of a pin 80.

The elongated clamping bar 6 projects the full lateral dimension of the blank B and is vertically movable by a plurality of vertically acting, synchronized cylinder and piston motors 81 having downwardly projecting piston rods 82. The lower ends of said piston rods 82 are provided with bearings 83 pivoted tp upwardly projecting hangers 84 of the clamp by means of pins 85.

It will be readily seen that by actuating the cylinder and piston motors 81, the clamping bar 6 can be brought downwardly firmly upon the sheet metal blank whereupon actuation of cylinder and piston motor 75 will tilt the table 5 upwardly to the vertical position and form a right angle bend in the blank.

The strap lock forming dies 9 and 10 are sub-stantially identical wherefore only the die 9 shown in FIG. 11 will be described in detail. Both dies are mounted on a rod 90 which projects in the fore and aft direction between the front and rear of the frame on the extreme left side of the frame. Each said die has a clamp portion 91 and an adjustable, threaded tightening rod 92 whereby said rod can be clamped in any suitable position fore and aft along the rod 90. Each die comprises a main body portion 93 having an upper plate 94 coextensive with the upper portion of the clamp portion 91. Each die 9 or 10 has a tiltable portion 89 pivoted between upstanding brackets 95 at journals 96 whereby when the outer end of said tiltable portion is raised, an inner end thereof closes in a jawlike fashion. The housing 93 contains suitable hydraulic means (not herein disclosed) including an upwardly projecting piston rod 97 adapted to exert vertical pressure on the outer end of the tiltable portion 89 to close the jaws at the opposite end thereof. Said jaws comprise an extension of the plate 94 having a wedge shaped male die portion 98 disposed thereon and adapted to interfit a female die cavity 99 at the inner end of the die. A stop 88 disposed inwardly of the die cavity projects upwardly fromthe plate 94 to limit the extent to which the sheet metal blank can be inserted. An ejector strip 87 is secured in any suitable manner to one of the brackets and curves downwardly below the female die cavity 99 whereby the new formed strap lock is ejected from said die cavity when the die opens. Thus when each die is closed, an offset strap lock D is formed in the metal a predetermined distance from the lateral edge of the blank by slitting the metal along a fore and aft line and punching the metal upwardly along one edge of the slit.

The cleat connector flange forming dies 11 and 12 are substantially identical except for the fact that they operate in opposite directions. As best seen in FIG. 4, each comprises a retractable, inner die forming portion 100 carried at a lateral edge of the table 5 and an extensible outer die forming portion 101 carried in a substantially vertical plane on the front of the frame 1.

The inner forming portion 100 comprises a strong steel plate which is relatively thin and forms, in effect, a lateral edge of the table 5. Each portion 100 is reciprocable in a slide 104 by means of a cylinder and piston motor 105 in a transverse direction. The initial lateral position of the portions 100 are shown in FIGS. 1, 2, and 4, whereby when the table is raised (FIG. 4), the outermost edges of said portions 100 are spaced only a slight distance from the outer flange forming portions 101.

An outer flange forming portion 101 is shown in FIG. 9, the same being made out of a rectangular bar which is formed to provide a triangular plane 106 having its base substantially adjacent to diagonally opposite corners at the lower end thereof and having its apex adjacent to one corner at the upper end thereof. The planes 106 are disposed at thefront and angle laterally and forwardly with the bases of the planes 106 at the bottom whereby as sheet metal which projects outwardly beyond the inner flange forming portions 100 is folded upwardly, the edge portion of the sheet metal will ride upwardly toward the peak or apex of the triangle and will be thus progressively bent to the right angle position shown in detail in FIG. 12. Thus the upward movement alone of the table 5 will form right angular flanges such as that shown in FIG. 12 at both lateral ends of the vertical wall 8 of the duct. 1

The outer flange forming portions 101 are secured t pairs of arms 107 which are connected at the front edges thereof by a plate 108. The arms 107 are pivotally secured'to the edges of a slide member 109 by bolts 110 with the plates 108 overlying an inner end portion of said slide member. Additional bolts 111 project through the openings in the plates 108 and are screw-thread fitted into the associated slide member 109. Coil compression springs 112 surround the bolts under the heads thereof and exert a substantial pressure against the plates 108 to urge the outer flange forming portions 101 to the positions illustrated.

The slide members 109 are movable inwardly from their normal position illustrated by means of slides or ways 113 and cylinder and piston motors 114 (FIGS. 1 and 4). Thus, with the inner and outer die forming portions in the positions shown in FIG. 12, the cylinder and piston motors 114 are actuated whereby the outer die forming portions 101 are moved inwardly to the position shown in FIG. 13 to complete backwardly folded cleat connector flanges as shown at F in FIGS. 13, 14, and 20. It will be readily seen that in this movement inwardly, the outer flange forming portions 101 can pivot slightly away from the flange being formed and accommodate to irregularities in the thickness of the folded flange and the inner flange forming portions 101 thereby preventing undue strain on or jamming of the dies 11 and 12.

FIG. 14 illustrates a manner in which both the inner flange forming portion 100 and the outer flange forming portions 101 are retracted to free the flanges F as the table 5 is moved back to the horizontal position. The inner flange forming portion 100 is retracted from its normal extended position to a retracted position whereas the outer flange forming portion returns from the extended position to its normal nonextended position. Thus the modular member M of FIG. 20 is formed with its major right angle bend, the two strap locks D, and the cleat connector flanges F. Additional formed portions such as a flange 115 and an edge fold 116, the latter affording an outwardly open slot, are presumed to be formed in a separate operation before forming by the machine of the present invention.

As viewed in FIG. 2 of the drawings, a blank B is positioned in the machine with one edge facing the operator, said one edge as herein illustrated having the flange 115 formed thereon (FIG. 20). The operator draws the blank B toward him (downwardly as seen in FIG. 2) until the edge rests against a pair of stop members 120 projecting upwardly above and immediately adjacent to the outer edge of the table 5. Lateral positioning of the blank B is accomplished by inserting the left-hand edge of said blank into the strap lock forming dies 9 and 10 until the lateral edge of said blank abuts the stops 88. Thus, the blank 13 is perfectly positioned to be folded upwardly by the table 5 after being firmly clamped by the clamping bar 6.

The stop members 120 are mounted to and move upwardly with the table during the forming operation. To prevent said stop members from dragging against and hanging onto the flanges 115 of the blank B when the table is lowered, means are provided for releasing or disengaging said stop members before the table pivots downwardly. Said stop members 120 are substantially identical in form and mechanical operation and only one of them will, therefore, be described in detail.

. Referring now particularly to FIGS. 4, 16, and 17, the

left-hand stop member 120 comprises a bracket 121 secured to a portion of the adjacent slide 104. Said bracket 121 projects outwardly slightly beyond the outer edge of the table 5 at which point a stop bar 122 is pivotally mounted by suitable means such as a pin 123. The stop bar 122 projects upwardly a short distance above the upper surface of the table 5 and has an inner edge adapted to contact the outer edge of said table. At the end of the bracket 121 opposite to the pin 123, said bracket has a downwardly projecting guide 125 through which an elongated rod 126 is slidably mounted. The rod 126 projects inwardly beyond the end of the guide 125 and projects outwardly or forwardly to the stop bar 122 to which it is pivoted by a pin 127 at a point below the pivot pin 123. A coil spring 128 connects the lowermost end of the stop bar 122, at a point below the pin 127, to the guide 125, at a point below the rod 126 whereby the stop bar 122 is normally biased at its upper end away from the outer edge of the table 5.

The cylinder and piston motor 105 has a piston rod 130 the outer end of which carries a block 131 fastened to a slidable portion 132 which carries and causes reciprocation of the inner flange forming portion 100. The inner end of the rod 126 is continuously biased against a side cam surface 133 of the block 131 by means of the coil spring 128. The cam surface 133 is beveled away from the edge of the table 5 in the direction of the inner flange forming portion as indicated at 133a whereby when said flange forming portion and the block 131 are retracted, the inner end of the rod 126 will ride inwardly on the bevel 133a thereby allowing the stop bar 122 to pivot away from the edge of the table 5. Thus, the stop bars 122 move away from the flange 115 of the blank B when the table 5 is in the upward position and before said table is lowered whereby any pressure of the stop bars against the blank is released and the table can move down freely without any tendency to pull or drag the blank with it. After the table has pivoted downwardly approximately half way, the cylinder and piston motors are actuated to extend the inner flange forming portions 100 to their normal position thereby moving the blocks 131 to the position illustrated in FIGS. 16 and 17 whereby the stop bars 122 return to their normal stop position against the outer edge of the table 5.

FIGS. 20 and 21 show the manner in which a second modular portion M (shown in broken lines in FIG. 20) is assembled with a first modular portion to form a completed ductwork section. Each flange is preferably provided with punched, spaced, offset locks 1 17, and each outwardly opening slot of the folds 116 is preferably provided with a backwardly turned lip 118 whereby said flange 115 can be inserted into the fold 116 and said locks 117 will engage the lip 118 to secure the modular members together.

FIG. 22 shows the manner in which the walls 7 of adjacent ductwork sections are engaged. An elongated, flattened S-shaped strap affords two oppositely opening slots each provided with a backwardly turned lip 191 similar to the lip 118 of the fold 116. Itwill be understood that a strap 190 extends the full width of the wall 7, one of the slots engaging the end of said wall 7 having the punched strap locks D, said locks D engaging the lip 191. The opposite, plain end of a wall 7 of another ductwork section is inserted intothe other slot of the strap 190 to complete the engagement between the walls of two sections.

It will be understood that both ends of the walls 7 may be provided with strap locks D for engaging lips 191, but this is not necessary because the walls 8 are securely fastened where the ductwork sections join by C-shaped cleats 195 engaging connector flanges F of one wall 8 and like flanges F of a wall 8 of the next adjacent section (FIG. 23). It will be understood that the cleats 195 extend the full width of the walls 8 and have a tight, drive fit whereby the ductwork sections are securely fastened together.

Referring now to the electrical diagrams of FIGS. 18 and 19, control means are provided for automatically folding the blank, punching the straps locks D, cross breaking one wall of the modular portion M, and forming the cleat connector flanges F. FIG. 19 shows switching means for energizing contact relay means including a pair of timer relays. FIG. 18 illustrates the solenoids whose energization is controlled by the relay contacts. The solenoids represent means for controlling valves in a hydraulic system in a known manner (not herein illustrated) whereby fluid is directed to the various cylinder and piston motors to cause extension or retraction of members controlled thereby. It will be understood that the present electrical diagram is greatly simplified and that many additional safety interlocks and overload safety devices of a known type, not herein illustrated, may be employed.

Referring now to the diagram of FIG. 19, a master control switch 140 is disposed in a line 141 connected across a pair of main leads L1 and L2. The master switch 140 is an On-Off switch adapted to completely disable the entire control system when in an Off position. Connected in series in the line 141 are a start switch 142, an emergency stop switch 143, and a motor relay MP which, when energized, starts a pump motor for building up hydraulic pressure. A timer relay TD2 is connected in parallel with the relay MP by means of a parallel line 144 connected between the start switch 142 and the lead L2. Normally open contacts MP-l controlled by the relay MP are disposed in a line 145 in parallel with the start switch 142, said contacts MP-l serving as hold-in contacts for both relays TD2 and MP after the start button has been released. v

The timer relay TD2 is of the On-Delay type and opens a pair of normally closed contacts TD2-1 in a line 146 (see bottom of FIG. 19) and closes a pair of normally open contacts TD2-2 in a line 147 (see bottom of FIG. 18) after a timed delay. The timer contacts TD2-1 control a circuit to a second timer TDl disposed in a line 148 connected to a main lead L2. The line 146 is connected to the lead L1 through the main starting line 141 between the start button 142 and the lead L2 whereby pressing of said start button also energizes the timer relay TDl. The timer contacts TD2-2 are disposed in series with a solenoid coil SV1 (FIG. 18) controlling a main hydraulic solenoid valve which, when actuated, releases pressure fluid to the system. Since the timer TD2 is of the On-Delay type, contacts TD2-2 will remain open for a timed period to delay energization of coil SVl, and contacts TD2-1 will remain closed for a timed period to energize the timer relay TDl. The main hydraulic solenoid valve is not actuated for a timed period after the motor and pump are started so that the pressure can build up with the pump in an unloaded condition.

The timer TD1 is of the Off-Delay type and controls a pair of normally closed contacts TD1-1 in a line 149 (FIG. 19) adapted to energize a first cylinder and piston motor relay CR1 controlling the cylinder and piston motor 20 (FIG. 1). Thus the contacts TD 1-1 immediately open to prevent immediate actuation of said cylinder and piston motor 20.

At the end of a timed period, relay TD2 times out thereby closing the contacts TD2-2 to actuate the solenoid SV1 and pressurize the hydraulic system. At the same time, contacts TD2-2 open to isolate the timer relay TD1 whereby timing out of said relay TD1 will again close the contacts TD1-1 in line 149. At this point it should be noted that a three-position Manual- Automatic-Off switch 150 has selector contacts 1500, 150b, and l50c effective in series with the line 147 (FIG. 18), 148, and 149, respectively. In the automatic position as illustrated, these contacts serve to complete circuits to the solenoid SV1, the timer TD1, and the relay CR1 to effect automatic operation of the machine as will hereinlater be fully described.

When a blank V is properly in the machine, the edge with the flange is brought forwardly against the stop members and the left-hand edge of the blank is inserted in the strap lock forming dies 9 and 10 as hereinbefore described. This initial placement of the blank actuates three normally open limit switches LS1, LS2, and LS3 disposed in series with relay CR1 and line 149. The limit switch LS1 is mounted to the strap lock forming die 10 and is actuated when the left-hand edge of the blank is inserted in said die. Limit switches LS2 and LS3 are disposed at the outer or forward edge of the table 5 whereby they are actuated by the forward edge of the blank. It will be noted that the limit switch LS3 has two pairs of normally open contacts, LS3-1 and LS3-2 and that it is the contacts LS3-l which are in series with the relay CR1. With the blank B actuating these three switches, a circuit is complete to relay CR1.

Energization of relay CR1 closes normally open hold-in contacts CR1-1 disposed in a line 152 connected in parallel around the limit switches LS1 and LS2 (FIG. 19). This also closes normally open contacts CR1-2 in a line 153 and normally closed contacts CR1-3 in a line 154 controlling valve solenoids SVZ-l and SV2-2 for respectively lowering and raising the cross break 4 (FIG. 18). Thus the solenoid SV2-1 actuates the cylinder and piston motor 20 to cause the cross break 4 to move downwardly. In a similar manner, the energized relay CR1 closes normally open contacts CR1-4 in a line 155 and opens normally closed contacts CR1-5 in a line 156 to energize a valve solenoid SV31 for causing the clamping bar 6 to move downwardly while de-energizing a valve solenoid SV3-2 which normally moves the clamping bar upwardly.

When the cylinder and piston motor 20 is actuated and the piston rod 30 thereof moved downwardly, a limit switch LS4 is closed by a trip 157 carried by said piston rod and projecting through a suitable opening in the inner housing 50. Limit switch LS4 is disposed in series with a relay coil CR2 in a line 158 (FIG. 19) disposed in parallel with the relay CR1 and the contact LS3-l of the limit switch LS3. Relay CR2 closes normally open contacts CR2-1 in a line 159 and opens normally closed concepts CR2-2 in a line 160 (FIG. 18) to energize a valve solenoid SV4-1 and de-energize a valve solenoid SV4-2. Also energized is a third valve solenoid SV5 disposed in a line 161 in parallel with the solenoid SV4-l. Energization of solenoid SVS actuates the strap lock forming dies 9 and 10 and energization of the solenoid SV4-1 actuates the cylinder and piston motors 75 to cause the table to move or pivot upwardly from the horizontal to the vertical position as shown in FIG. 15.

When the table 5 pivots to the vertical position it closes a normally open limit switch LS5 on the front of the machine (FIG. 1). LS5 completes a circuit across a line 162 through normally closed contacts CRX-1 to energize a relay coil CR3 (FIG. 19). This closes normally open contacts CR3-1 and opens normally closed contacts CR32 in lines 163 and 164 (FIG. 18) to energize a valve solenoid SV6-1 and de-energize a solenoid SV6-2, respectively. The solenoid SV6-1 actuates the cylinder and piston motors 114 whereby the outer flange forming die portions 101 move inwardly, as from the position shown in FIG. 12 to the position shown in FIG. 13, to complete the fold of the cleat connector flanges F.

As shown in FIG. 1, the right-hand cylinder and piston motor 114 is connected at its piston rod 165 to the associated slide member 109 by a block 166 which serves as a trip for a pair of limit switches LS6 and LS8. When the cylinder and piston motors are actuated, the block 116 trips and closes the limit switch LS6 which is disposed in a line 167 whereby it energizes a relay coil CR4 (FIG. 19). Relay CR4 closes normally open contacts CR4-1 and opens normally closed contacts CR4-2 in lines 168 and 169 to energize a valve solenoid SV7-1 and de-energize a valve solenoid SV7-2, respectively (FIG. 18). Solenoid SV7-l actuates the cylinder and piston motors 105 to retract the inner flange forming die portions 100 whereby they are moved inwardly from the position as illustrated in FIG. 13 to the position as illustrated in FIG. 14 to disengage them from the cleat connector flanges F. This causes the retracting block 131 to trip and close a normally open limit switch LS7 disposed in a line 170 to energize a relay coil CRX. Relay CRX opens the aforementioned normally closed contacts CRX-1 in line 162 to de-energize the relay CR3 while at the same time closing normally open contacts CRX-2 in line 148 to energize the timer relay TD1.

When the relay CR3 is de-energized, it will be readily seen that the normally open contacts CR3-1 open to isolate the solenoid SV6-1 and that the normally closed contacts CR3-2 close to energize the solenoid SV6-2. The result of this is that the cylinder and piston motors 1 14 are actuated to return the outer flange forming dies 100 to their outermost position, this action causing the block 166 to trip and close normally open limit switch LS8 in line 148. It will be understood that limit switch LS8 was previously closed whenever the outer flange forming die portions 100 were in their retracted position, but this has no effect on the timer TD1 due to the normally open contacts CRX-2. However, with the inner flange forming portions 100 now being retracted thereby closing limit switch LS7 and energizing coil CRX, contacts CRX-2 are closed and a circuit is completed to the timer TD1. Timer TD1, being of the Off-Delay type, immediately opens aforementioned normally closed contacts TD 1-1 in line 149 and closes normally open contacts TD 1-2 in a line 171 in parallel with the second pair of contacts LS3-2 of the limit switch LS3 disposed in a line 172. The line 171 is connected into the line 149 between the contacts 1500 of the selector switch and the contacts TD1-1 of the timer TD1. The line 172 is connected into the line 167 between the limit switch LS6 and the coil CR4. Normally open contacts CR4-3 are also disposed in the line 172 whereby when the coil CR4 is energized by closing of the limit switch LS6, normally open contacts CR4-3 close to form a hold-in circuit through the now closed second contacts LS3-2 of the limit switch'LS3. Thus, the relay CR4 is provided with a hold-in circuit as long as the blank holds the limit switch LS3 closed with an additional circuit being formed as soon as the timer TD1 is energized. However, opening of the contacts TD11 of the timer TD1 immediately breaks the circuit to the relays CR1, CR2, CR3, and CRX de-energizing them. The result is that the cylinder and piston motor 20 is actuated by solenoid SV2-2 to raise the cross break device 4, the cylinder and piston motors 81 are actuated by solenoid SV3-2 to raise the clamping bar 6, the normally open strap lock forming dies release the blank, the cylinder and piston motors are actuated by solenoid SV4-2 to lower the table, and the circuit is broken to the Off-Delay timer TD1 by opening of the contacts CRX-2. As the table 5 lowers, limit switch LS3 will move away from the now upturned edge of the blank thereby allowing the contacts LS3-2 to return to their normally open position. However, the circuit to the relay CR4 is maintained through the contacts TD1-2 which remain closed for a timed period beginning with the de-energization of the Off-Delay timer relay TD1. The energized relay CR4 maintains energization of the solenoid SV7-1 for the timed period of relay TD1 whereby the inner flange forming portions remain in their retracted position until the table has pivoted downwardly a substantial distance to assure that these flange forming portions are clear of the inturned cleat connector flanges F. When the timer TD1 times out, contacts TD 1-2 open thereby de-energizing the relay CR4 and returning the inner flange forming portions 100 to their extended or initial position. At the same time, normally closed contacts TD1-1 close but no circuit is formed due to the fact that at this point the limit switches LS2 and LS3 are open. The operator thus removes the formed modular member and inserts a new blank into the machine whereupon the machine will automatically perform the foregoing operations described.

Because de-energization of the relays energizes respective solenoids to return all cylinder and piston motors to their initial position, upon initial start-up of the machine with no material in the machine, any cylinder and piston motor out of proper initial position will return to the starting position.

When the selector switch is turned to the manual position, and the master control switch is turned to the On position, the timer TD1 is energized whereby the contacts TD1-1 will open to assure de-energization of the relays and return of all members to their initial position. In the manual position, all of the relays are bypassed for controlling the cylinder and piston motors whereby individual selector switches 180, 181, 181', 182, 182', 183, 183' and 184, 184' connected in parallel with the relay contacts from a common line 185 (FIG. 18) can be individually actuated to operate the cylinder and piston motors 20, 81, 75, 114, and 105, respectively, in addition to actuation of the strap lock forming dies in conjunction with actuating the cylinder and piston motors 75 of the table. Returning the selector switch to the automatic position will, as set forth above, return any out of position cylinder and piston motor to its proper starting position. In either the automatic or manual position, the main hydraulic valve solenoid SVl is energized only after the pump motor has been running for sufficient length of time to bring the hydraulic pressure to the desired level and to assure that each start of the pump motor will be unloaded. If material left in the machine after individual manual operation is in the proper position whereby all three of the table switches LS1, LS2, and LS3 are closed, then movement .of the selector switch to automatic will cause the machine to finish out the operation. Out of position cylinders will assume a proper position and conclude the sequence of the automatic cycle.

It will be understood that many changes in the details of the invention may be made without, however, departing from the spirit thereof or the scope of the appended claims.

I claim:

1. In a machine for forming sheet metal ductwork, a supporting frame; means providing a flat bed on said frame; said frame having a pivoted table portion coplanar with said bed in a lowered position and pivotable to a position perpendicular to said bed; elongated clamping means for clamping a sheet metal blank to said bed adjacent to said table, whereby upon pivoting said table upwardly, said blank is bent to an L-shape to form two right angularly disposed, substantially rectangular walls, a first wall overlying said bed and a second wall projecting perpendicularly from one edge of said first wall; and a press forming device mounted above said bed having a portion movable downwardly to impress a crown in the first wall to stiffen the first wall.

2. In a machine for forming sheet metal ductwork as set forth in claim 1: means providing a tough elastic surface on said flat bed; said press forming device comprising a vertical columnar structure; a plurality of blades disposed in substantially vertical planes and having crease forming lower edges disposed against said first wall; means mounting one end of each said blade to a portion of said columnar structure, said blade extending symmetrically outwardly from said columnar structure whereby downward pressure thereon impresses symmetrically arranged creases in the metal and forms a slight crown on the bottom of the first wall; and power means for applying a substantial downward force to said portion of said columnar structure to which said blades are secured.

3. In a machine for forming sheet metal ductwork as set forth in claim 2: said means mounting one end of each blade affording slight pivotal movement thereof in a vertical direction; longitudinally adjustable means connecting an outer end portion of each said blade to said columnar structure, each said adjustable means being angled downwardly from its point of connection at said columnar structure to its point of connection at said blade whereby to regulate the relative pressure between the inner and outer end of each said blade by adjusting the length of said adjustable means.

4. In a machine for forming sheet metal ductwork as set forth in claim 3: there being four of said blades carried by said columnar structure, said blades being arranged symmetrically in pairs on either side of center lines disposed at right angles to each other in a plane parallel with the one wall and intersecting the axis of said columnar structure, said blades being angled with respect to each other to substantially an X-shape; said longitudinally adjustable means being adjusted to provide slightly less pressure on said blades at the outer ends thereof than at the inner ends thereof whereby when said press forming device is actuated, a slightly frustopyramidal crown is formed on the bottom of the first wall.

5. In a machine for forming sheet metal ductwork as set forth in claim 4: said means mounting one end of each said blade to a portion of said columnar structure comprising axially vertical bearing means allowing pivoting of each said blade in horizontal plane; a pair of horizontally disposed, oppositely projecting guide bars secured at one end thereof to said portion of said columnar structure and disposed parallel with said clamping means between oppositely laterally projecting, outwardly diverging pairs of said blades; a link pivoted at one end thereof to each said blade adjacent to the outer end of the blade, the links of each said pair of blades having the inner ends thereof pivoted to each other and slidably engaged in an elongated slot in the adjacent guide bar whereby the pivoting of one blade of a pair in a horizontal direction causes opposite pivotal movement of like extent in the other blade of said pair; and means holding the outer end of that blade of each pair which is disposed adjacent to said clamping means whereby movement of said columnar structure away from said clamping means causes said pairs of blades to spread apart symmetrically to a greater extent and opposite movement of said columnar structure causes said pairs of blades to close.

6. In a machine for forming sheet metal dctwork as set forth in claim 5: said power means comprising a cylinder and piston motor mounted on guideways for fore'and aft movement perpendicular to said table and clamping means, said columnar structure depending from said cylinder and piston motor; and means for adjusting said cylinder and piston motor along said guideways.

7. In a machine for forming sheet metal ductwork as set forth in claim ll: means providing a tough elastic surface on said first bed; said press forming device comprising a cylinder and piston motor mounted on a support a substantial distance above said flatbed; a tubular noncircular housing secured at one end to said support coaxial with said motor and depending from said support; said motor having a piston rod extending downwardly through said housing and projecting below the lower end of said housing; an outer noncircular housing of shorter axial dimension than said first mentioned housing slidably telescoped over said first mentioned housing, said housings being nonrotatable with respect to each other; means securing the lower end of said piston rod to said outer housing; means mounting inner ends of four crease forming blades to said outer housing, said blades being symmetrically arranged to impress a substantially X-shaped crown in the one wall of the blank.

8. In a machine for forming sheet metal ductwork as set forth in claim 7: said means mounting the inner ends of said blades comprising axially vertical bearing means mounting said blades for horizontal pivotal movement, there being sufficient play in said bearing means to afford slight up and down movement of the outer ends of said blades; a longitudinally adjustable rocl connecting the outer end portion of each said blade with an upper portion of said outer housing whereby said rods extend outwardly and angle downwardly and afford means for adjusting the relative pressure on the blank between the inner and outer ends of said blades when said motor is actuated.

9. In a machine for forming sheet metal ductwork as set forth in claim 8: a pair of horizontally disposed, op positely projecting, elongated guide bars secured at one end thereof to said outer housing and disposed parallel with said clamping means between oppositely laterally projecting, outwardly diverging pairs of said blades; and a link pivoted at one end of each said blade adjacent to the outer end of the blade, the links of each said pair of blades having the inner ends thereof pivoted to each other and slidably engaging an elongated, longitudinally directed slot in the adjacent guide bar whereby the pivoting of one blade of a pair in a horizontal direction causes opposite pivotal movement of like extent in the other blade of said pair.

10. In a machine for forming sheet metal ductwork as set forth in claim 9: said frame including horizontal guideways extending perpendicular to said clamping means and table in a fore and aft direction; means mounting said support for sliding movement of said cylinder and piston motor on said guideways; means for moving said support along said guideways; means holding the outer end of that blade of each pair which is disposed adjacent to said clamping means whereby movement of said support and cylinder and piston motor in the aft direction away from said clamping means causes said pairs of blades to spread apart symmetrically to widen the X-shaped crown and whereby opposite movement of said support and cylinder and piston motor causes said pairs of blades to symmetrically close to narrow the X-shaped crown.

11. In a machine for forming sheet metal ductwork as set forth in claim 1: die means provided adjacent to at least one lateral side of said table and on said frame forming a cleat connector flange at said one side edge of the second wall when said table is pivoted to said perpendicular position; said die means comprising an inner flange forming portion in the form of a flat, relatively thin member projecting laterally from one end of said table and having a straight outer edge perpendicularto said clamping means; an outer flange forming portion carried by said frame and comprising a bar member so positioned that when said table is folded upwardly, the edge of said inner flange forming portion is disposed closely adjacent to an edge of said bar member, a portion of the blank projecting outwardly beyond the edge of said inner flange forming portion whereby it is bent forwardly at right angles upon contact with said edge of said bar member; means for mounting said outer flange forming portion for reciprocating movement parallel with said clamping means whereby said bar member can be moved inwardly in overlapping relationship with said inner flange forming portion to bend the edge of the blank at one end of said second wall to complete a cleat connector flange; means for mounting said inner flange forming portion for reciprocating movement parallel with the movement of said outer flange forming portion whereby both said portions can be retracted to disengage them from the cleat connector flange and allow the table to pivot downwardly.

12. In a machine for forming sheet metal ductwork as set forth in claim 11: said outer flange forming portion being so shaped as to provide a triangular plane having its base at the bottom of said bar member and converging upwardly to the top of said bar member, said plane being angled forwardly and laterally outwardly with respect to the inner flange forming portion whereby the outwardly extending portion of the blank which projects laterally beyond the inner flange forming portion first strikes the broad base of the plane as it pivots upwardly and is progressively formed by said plane and the edge of said bar member to a position at right angles with the main portion of the second wall.

13. In a machine for forming sheet metal ductwork as set forth in claim 12: said means mounting said outer flange forming portion for reciprocating movement comprising a slide member; power means for reciprocating said slide member; means pivotally mounting said bar member to one end of said slide member for pivoting about a vertical axis disposed adjacent to the inner end of said slide member; and resilient means strongly urging said bar member into alignment with said slide member and allowing said bar member to pivot outwardly a slight amount as it slides over the inner flange forming portion to form the cleat.

14. In a machine for forming sheet metal ductwork as set forth in claim 13: said machine having said die means provided adjacent to both lateral sides of said table, both die means acting laterally inwardly to form inwardly turned cleat connector flanges at both side edges of the second wall.

15. In a machine for forming sheet metal ductwork as set forth in claim 1: stop means carried at the outer edge of said pivoted table portion and projecting thereabove, against which the forward edge of the blank abuts to properly position the blank in the fore and aft direction prior to said clamping means clamping the sheet metal blank to said bed.

16. In a machine for forming sheet metal ductwork as set forth in claim 15: said stop means comprising at least two stop members disposed in spaced relationship upon the forward edge of said table; each said stop member being elongated andv disposed substantially vertically against the forward edge of said table, the upper portion of said stop member projecting downwardly a substantial distance below said table; bracket means carried by said table and pivotally mounting each said stop member at a medial portion thereof below the level of said table; and means adapted to hold the upper end portion of each said stop member against the forward edge of said table for initial positioning of the blank and during the upward pivoting movement of said table and for pivoting the upper end of said stop member away from the table edge and away from the blank when said table is in its upper position whereby to release the edge of said blank before the table is lowered back to its level position.

17. In a machine for forming sheet metal ductwork as set forth in claim 16: said means for holding and pivoting said stop members each comprising a rod disposed below said bracket means and oriented in the fore and aft direction, the forward end of said rod being pivotally connected to said stop member below the pivot of said bracket means; apertured guide means slidably receiving said rod rearwardly of the pivoted end of said rod; means biasing the lowermost end portion of said stop member in a rearward direction whereby the upwardly projecting end portion of said stop member is biased away from the forward edge of said table; a cam member abutting the rearwardly directed end of said rod and pressing said rod forwardly whereby the upper end portion of said stop member is held adjacent to the forward edge of said table; said cam member having a cam surface portion allowing said rod to move rearwardly whereby the upper end portion of said stop member is allowed to pivot forwardly away from the forward edge of said table; and power means for moving said cam whereby said surface portion abuts the end of the rod after the table has been pivoted to its uppermost position.

18. In a machine for forming sheet metal ductwork as set forth in claim 1: said table having stop means against which a forward edge of the blank abuts to initially position the blank in a forward direction; offset strap lock forming die means mounted on said frame adjacent to one lateral edge of said bed and having fixed and vertically movable jaws between which a side edge portion of the blank rearwardly of said clamping means is disposed; said strap lock forming die means having stop means associated therewith for positioning the adjacent side edge of the blank prior to punching offset strap locks therein; and power means for actuating said strap lock forming die means.

19. In a machine for forming sheet metal ductwork as set forth in claim 18: means mounting said strap lock forming dies comprising a fore and aft disposed shaft carried by said frame; and clamp means for adjustably positioning each said strap lock forming die along said shaft.

20. In a machine for forming modular portions of ductwork from sheet metal blanks, a supporting frame having a flat bed; means providing a tough, elastic surface on said bed; said frame having a table portion pivoted at its inner edge and disposed coplanar with and extending from said bed in a lowered position and pivotable to a position perpendicular to said bed; an elongated clamping bar for clamping the blank to said bed along a line parallel with and closely adjacent to said inner edge of said table whereby upward pivoting of said table bends the blank about said clamp to an L- shape and forms two right angularly disposed, substantially rectangular walls, one of the walls overlying said bed; a pair of inner flange forming die members mounted at the side edges of said table perpendicular to the axis of said table; a pair of outer flange forming die members carried by said frame and affording shaping means against which portions of said blank projecting laterally beyond said inner flange forming die members at the side edges of said table are pressed and bent to right angles when said table is pivoted upwardly; said outer flange forming die members being movable laterally inwardly over said inner flange forming die members to complete backwardly turned cleat connector flanges; said inner flange forming die members being retractable whereby they are disengaged from said connector flanges to allow said table to return to the horizontal position; a press forming device carried by said frame above the one wall of the blank, said device being movable downwardly for impressing a slight, frustopyramidal crown in the one wall; said modular portion adapted to be assembled with a like modular portion to provide a section of rectangular ductwork having two parallel, opposite crowned walls and two parallel, opposite plain walls.

21. In a machine for forming modular portions as set forth in claim 20: stop means carried at the outer, forward edge of said table portion and projecting thereabove, the forward edge of the blank abutting said stop to properly position the blank in the fore and aft direction prior to clamping the blank to said bed.

22. In a machine for forming modular portions as set forth in claim 21: said stop means comprising at least two stop members disposed in spaced relationship upon the forward edge of said table; each said stop member being elongated and disposed substantially vertically against the forward edge of said table, a lower portion of each stop member projecting downwardly a substantial distance below said table; bracket means carried by said table and pivotally mounting said stop member at a medial portion thereof below the level of said table; and means adapted to hold the upper end portion of said stop member against the forward edge of said table for initial positioning of the blank and during the upward pivoting movement of said table and for pivoting the upper end of said stop member away from the table edge and away from the blank when said table is in its upper position whereby to release the edge of said blank before the table is lowered back to its level position.

23. In a machine for forming modular portions as set forth in claim 22: said means for holding and pivoting each said stop member comprising a bracket carried by said table means, said bracket providing a pivoted connection for a medial portion of said stop member below the level of said table; a rod disposed below said bracket and oriented in the fore and aft direction, the forward end of said rod being pivotally connected to said stop member below the pivot of said bracket; apertured guide means slidably receiving said rod rearwardly of the pivoted end of said rod; means biasing the lowermost end portion of said stop member in a rearward direction whereby the upwardly projecting end portion of said stop member is biased away from the forward edge of said table; means for retracting said inner flange forming die members, each including cam means abutting the rearwardly directed end of one rod of one of said stop means and pressing said rod forwardly whereby the upper end portion of the associated stop member is held adjacent to the forward edge of said table; each said cam member having a cam surface portion allowing the associated rod to move rearwardly when the inner flange forming die members are retracted whereby the upper end portion of each said stop member is allowed to pivot away from the forward edge of the table at the same time that the inner flange forming die members are disengaged from the cleat connector flanges.

24. In a machine for forming modular portions as set forth in claim 20: said press forming device comprising a cylinder and piston motor mounted on a support a substantial distance above said flat bed; a tubular noncircular housing secured at one end to said support coaxial with said motor and depending from said support; said motor having a piston rod extending downwardly through said housing and projecting below the lower end of said housing; an outer noncircular housing of shorter axial dimension than said first mentioned housing slidably telescoped over said first mentioned housing, said housings being nonrotatable with respect to each other; means securing the lower end of said piston rod to said outer housing; means mounting inner ends of four crease forming blades to said outer housing, said blades being symmetrically arranged to impress a substantially X-shaped crown in the one wall of the blank.

25. In a machine for forming modular portions as set forth in claim 24: said means mounting the inner ends of said blades comprising axially vertical bearing means mounting said blades for horizontal pivotal movement, there being sufficient play in said bearings to afford slight up and down movement of the outer ends of said blades; a longitudinally adjustable rod connecting the outer end portion of each said blade with an upper portion of said outer housing whereby said rods extend outwardly and angle downwardly and afford means for adjusting the relative pressure on the blank between the inner and outer ends of said blades when said motor is actuated.

26. In a machine for forming modular portions as set forth in claim 25: a pair of horizontally disposed, oppositely projecting, elongated guide bars each secured at one end thereof to said outer housing and disposed parallel with said clamping bar between oppositely laterally projecting, outwardly diverging pairs of said blades; and a link pivoted at one end to each said blade adjacent to the outer end of the blade, the links of each said pair of blades having the inner ends thereof pivoted to each other and slidably engaging an elongated, longitudinally, directed slot in the adjacent guide bar whereby the pivoting of one blade of a pair in a horizontal direction causes opposite pivotal movement of like extent in the other blade of said pair.

27. In a machine for forming modular portions as set forth in claim 26: said frame including horizontal guideways extending perpendicular to said clamping means and table in a fore and aft direction; means mounting said support for sliding movement of said cylinder and piston motor on said guideways; means for moving said support along said guideways; means holding the outer end of that blade of each pair which is disposed adjacent to said clamping means whereby movement of said support and cylinder and piston motor in the aft direction away from said clamping means causes said pairs of blades to spread apart symmetrically to widen the X-shaped crown and whereby opposite movement of said support and cylinder and piston motor causes said pairs of blades to symmetrically close to narrow the X-shaped crown.

28. A cross break device for impressing a slightly frustopyramidal crown in a wall of sheet metal ductwork during the forming thereof, said cross break device mounted upon a frame having a flat bed; means providing a tough elastic surface on said flat bed; said cross break device comprising a cylinder and piston motor mounted on a support a substantial distance above said flat bed; a tubular noncircular housing secured at one end to said support coaxial with said motor and depending from said support; said motor having a piston rod extending downwardly through said housing and projecting below the lower end of said housing; an outer noncircular housing of shorter axial dimension than said first mentioned housing slidably telescoped over said first mentioned housing, said housings being nonrotatable with respect to each other; means securing the lower end of said piston rod to said outer housing; means mounting inner ends of four crease forming blades to said outer housing, said blades being symmetrically arranged to impress a substantially X-shaped crown in the sheet metal.

29. In a cross break device as set forth in claim 28: said means mounting the inner ends of said blades comprising axially vertical bearing means mounting said blades for horizontal pivotal movement, there being sufficient play in said bearing means to afford slight up and down movement of the outer ends of said blades; a longitudinally adjustable rod connecting the outer end portion of each said blade with an upper portion of said outer housing whereby said rods extend outwardly and angle downwardly and afford means for adjusting the relative pressure on the sheet metal between the inner and outer ends of said blade when said motor is actuated.

30. In a cross break device as set forth in claim 29: a pair of horizontally disposed, oppositely projecting, elongated guide bars secured at one end thereof to said outer housing and disposed between oppositely laterally projecting, outwardly diverging pairs of said blades; and a link pivoted at one end to each said blade adjacent to the outer end of the blade, the links of each said pair of blades having the inner ends thereof pivoted to each other and slidably engaging an elongated, longitudinally directed slot in the adjacent guide bar whereby the pivoting of one blade of a pair in a horizontal direction causes opposite pivotal movement of like extent in the other blade of said pair.

31. In a cross break device as set forth in claim 30: said frame including horizontal guideways extending perpendicular to said table in a fore and aft direction; means mounting said support for sliding movement of said cylinder and piston motor on said guideways; means for moving said support along said guideways; means for holding the outer end of one blade of each pair disposed on the same side of said cross break device whereby movement of said support and cylinder and piston motor in the direction of said guideways away from said holding means causes said pairs of blades to spread apart symmetrically to widen the X- shaped crown and whereby opposite movement of said support and cylinder and piston motor causes said pairs of blades to symmetrically close to narrow the X- shaped crown.

32. In a machine for forming sheet metal ductwork wherein the machine has a frame, a horizontal bed, clamping means adjacent to one edge for clamping a sheet metal blank, and a pivoted table disposed adjacent to the one edge coplanar with the bed when in a lowered position and pivotable upwardly to form a right angularly disposed wall; die means for forming cleat connector flanges at the vertical side edges of the edge of the blank wall comprising inner flange forming portions in the form of flat, relatively thin members projecting laterally from the ends of the table and having straight outer edges; outer flange forming portions carried by said frame and comprising bar members so positioned that when said table is folded upwardly, the edges of said inner flange forming portions are disposed closely adjacent to the edges of said bar members, a portion of the blank projecting outwardly beyond the edges of said inner flange forming portions and being bent forwardly at right angles upon contact with said edges of said bar members; means for mounting each said outer flange forming portion for reciprocating movement parallel with said clamping means whereby said bar members can be moved inwardly in overlapping relationship with said inner flange forming portions to bend the lateral edges of the blank to complete the cleat connector flanges; means for mounting said inner flange forming portion for reciprocating movement parallel with the movement of said outer flange forming portions whereby both said portions can be retracted to disengage them from the cleat connector flanges and allow the table to pivot downwardly.

33. In a machine as set forth in claim 32: each said outer flange forming portion being so shaped as to provide a triangular plane having its base at the bottom of the bar member and converging upwardly to the top of said bar member, said plane being angled forwardly and laterally outwardly with respect to the inner flange forming portion whereby the outwardly extending portion of the blank which projects laterally beyond the inner flange forming portion first strikes the broad base of the plane as it pivots upwardly and is progressively formed by said plane and the edge of said bar member to a position at right angles with the main portion of the wall.

34. In a machine as set forth in claim 32: said means mounting said outer flange forming portion for reciprocating movement comprising a slide member; power means for reciprocating said slide member; means pivotally mounting said bar member to one end of said slide member for pivoting about a vertical axis disposed adjacent to the inner end of said slide member; and resilient means strongly urging said bar member into alignment with said slide member and allowing said bar member to pivot outwardly a slight amount as it slides over the inner flange forming por tion to form the cleat.

35. In a machine as set forth in claim 32: stop means carried at the outer edges of said pivoted table portion and projecting'thereabove for positioning a forward of sheet metal; said stop means comprising at least two stop members disposed in spaced relationship upon the outer edge of said table; each said stop member being elongated and disposed substantially vertically against the forward edge of said table; a lower portion thereof projecting downwardly a substantial distance below said table; bracket means carried by said table and pivotally mounting said stop member at a medial portion thereof below the level of said table; a rod disposed below said bracket means and oriented perpendicular to the outer edge of said table, the outer end of said rod being pivotally connected to said stop member below the pivot of said bracket means; apertured guide means slidably receiving said rod spaced inwardly of the said outer edge of said table; means biasing the lowermost end portion of said stop member inwardly whereby the upwardly projecting end portion of said stop member is biased away from the forward edge of said table; said means for mounting said inner flange forming portion including a cam abutting the inwardly directed end of said rod and pressing said rod forwardly whereby the upper end portion of each said stop member is held adjacent to the forward edge of said table; said cam member having a cam surface portion allowing said rod to move inwardly whereby the upper end portion of said stop member is allowed to pivot away from the forward edge of said table; said cam surface portion being moved into alignment with said rod when said inner flange forming portions are retracted thereby freeing the edge of the sheet metal.

36. In a machine for forming modular portions of sheet metal ductwork from a sheet metal blank, a frame; said frame having a flat bed; means providing a resilient surface on said bed; a vertically movable, elongated clamping bar disposed above said bed adjacent to and parallel with one edge thereof; power means for actuating said clamping bar; a pivoted table mounted on said frame adjacent to said one edge and pivotable upwardly from a horizontal to a vertical position whereby to bend a sheet metal blank held at a midportion thereof by said clamping bar to form horizontal and vertical walls; power means for actuating said table; a vertically acting press forming device mounted above said bed for impressing a slight crown in the horizontal wall; power means for actuating said press forming device; a pair of inner flange forming die members carried by, and comprising straight lateral side edges of, said table; outer flange forming die members carried by said frame and having straight edges disposed closely adjacent to said side edges of said inner flange forming die members when said table is raised, the blank projecting laterally beyond said table and being pressed against said outer die members and bent at right angles when said table is pivoted to the vertical position; power means for reciprocating said outer die members whereby they can be moved inwardly over said inner die members to complete backw ardly turned cleat connector flanges at the lateral edges of said vertical wall; power means for reciprocating said inner die members for disengagement from the cleat connector flanges; a pair of stop bars pivotally mounted adjacent to the outer nonpivoted edge of said table for positioning a forward edge of the blank, portions of each bar projecting above and below said table; cam and cam follower means associated with said stop bars and said power means of said inner die members whereby said inner die members are retracted for disengagement from the cleat connector flanges concurrently with pivoting of said stop bars away from said outer table edge to clear the edge of the vertical wall; and electrical control means causing said clamping bar to clamp the blank to said bed, said press forming device to lower and impress the horizontal wall, said table to pivot upwardly to form the vertical wall and bend the lateral edge portions thereof at right angles, said outer die members to extend and complete the cleat connector flanges, both said inner and outer die members to retract and said stop bars to pivot away from said outer edge of said table, said table to return to a horizontal position, and said clamping bar and press forming device to raise, in an automatic series of sequential and concurrent operations.

37. In a machine as set forth in claim 36: said control means including a single relay means for causing said clamping bar and press forming device to lower; and means responsive only to the lowering of said press forming device for causing said table to pivot upwardly whereby said table is not actuated until after the blank is firmly gripped by said clamping bar and press forming device.

38. In a machine as set forth in claim 37: said control means including means responsive only to said table being pivoted upwardly causing said outer die members to move inwardly to complete the cleat connector flanges.

39. In a machine as set forth in claim 38: said control means including .means responsive to said outer die members moving inwardly causing said inner die members to retract and said stop bars to pivot away from the forward edge of the blank and said outer edge of said table.

40. In a machine as set forth in claim 39: said control means including means responsive to said inner die members retracting causing said outer die members to retract, said table to return to a horizontal position, and said clamping bar and press forming device to rise; said control means including means delaying the return of said inner die members to the extended position until said table has pivoted downwardly at least partway to assure that said inner die members and stop bars clear the cleat connector flanges and upper edge of the vertical wall. 

1. In a machine for forming sheet metal ductwork, a supporting frame; means providing a flat bed on said frame; said frame having a pivoted table portion coplanar with said bed in a lowered position and pivotable to a position perpendicular to said bed; elongated clamping means for clamping a sheet metal blank to said bed adjacent to said table, whereby upon pivoting said table upwardly, said blank is bent to an L-shape to form two right angularly disposed, substantially rectangular walls, a first wall overlying said bed and a second Wall projecting perpendicularly from one edge of said first wall; and a press forming device mounted above said bed having a portion movable downwardly to impress a crown in the first wall to stiffen the first wall.
 2. In a machine for forming sheet metal ductwork as set forth in claim 1: means providing a tough elastic surface on said flat bed; said press forming device comprising a vertical columnar structure; a plurality of blades disposed in substantially vertical planes and having crease forming lower edges disposed against said first wall; means mounting one end of each said blade to a portion of said columnar structure, said blade extending symmetrically outwardly from said columnar structure whereby downward pressure thereon impresses symmetrically arranged creases in the metal and forms a slight crown on the bottom of the first wall; and power means for applying a substantial downward force to said portion of said columnar structure to which said blades are secured.
 3. In a machine for forming sheet metal ductwork as set forth in claim 2: said means mounting one end of each blade affording slight pivotal movement thereof in a vertical direction; longitudinally adjustable means connecting an outer end portion of each said blade to said columnar structure, each said adjustable means being angled downwardly from its point of connection at said columnar structure to its point of connection at said blade whereby to regulate the relative pressure between the inner and outer end of each said blade by adjusting the length of said adjustable means.
 4. In a machine for forming sheet metal ductwork as set forth in claim 3: there being four of said blades carried by said columnar structure, said blades being arranged symmetrically in pairs on either side of center lines disposed at right angles to each other in a plane parallel with the one wall and intersecting the axis of said columnar structure, said blades being angled with respect to each other to substantially an X-shape; said longitudinally adjustable means being adjusted to provide slightly less pressure on said blades at the outer ends thereof than at the inner ends thereof whereby when said press forming device is actuated, a slightly frustopyramidal crown is formed on the bottom of the first wall.
 5. In a machine for forming sheet metal ductwork as set forth in claim 4: said means mounting one end of each said blade to a portion of said columnar structure comprising axially vertical bearing means allowing pivoting of each said blade in horizontal plane; a pair of horizontally disposed, oppositely projecting guide bars secured at one end thereof to said portion of said columnar structure and disposed parallel with said clamping means between oppositely laterally projecting, outwardly diverging pairs of said blades; a link pivoted at one end thereof to each said blade adjacent to the outer end of the blade, the links of each said pair of blades having the inner ends thereof pivoted to each other and slidably engaged in an elongated slot in the adjacent guide bar whereby the pivoting of one blade of a pair in a horizontal direction causes opposite pivotal movement of like extent in the other blade of said pair; and means holding the outer end of that blade of each pair which is disposed adjacent to said clamping means whereby movement of said columnar structure away from said clamping means causes said pairs of blades to spread apart symmetrically to a greater extent and opposite movement of said columnar structure causes said pairs of blades to close.
 6. In a machine for forming sheet metal dctwork as set forth in claim 5: said power means comprising a cylinder and piston motor mounted on guideways for fore and aft movement perpendicular to said table and clamping means, said columnar structure depending from said cylinder and piston motor; and means for adjusting said cylinder and piston motor along said guideways.
 7. In a machine for forming sheet metal ductwork as set forth in claim 1: means provIding a tough elastic surface on said first bed; said press forming device comprising a cylinder and piston motor mounted on a support a substantial distance above said flat bed; a tubular noncircular housing secured at one end to said support coaxial with said motor and depending from said support; said motor having a piston rod extending downwardly through said housing and projecting below the lower end of said housing; an outer noncircular housing of shorter axial dimension than said first mentioned housing slidably telescoped over said first mentioned housing, said housings being nonrotatable with respect to each other; means securing the lower end of said piston rod to said outer housing; means mounting inner ends of four crease forming blades to said outer housing, said blades being symmetrically arranged to impress a substantially X-shaped crown in the one wall of the blank.
 8. In a machine for forming sheet metal ductwork as set forth in claim 7: said means mounting the inner ends of said blades comprising axially vertical bearing means mounting said blades for horizontal pivotal movement, there being sufficient play in said bearing means to afford slight up and down movement of the outer ends of said blades; a longitudinally adjustable rod connecting the outer end portion of each said blade with an upper portion of said outer housing whereby said rods extend outwardly and angle downwardly and afford means for adjusting the relative pressure on the blank between the inner and outer ends of said blades when said motor is actuated.
 9. In a machine for forming sheet metal ductwork as set forth in claim 8: a pair of horizontally disposed, oppositely projecting, elongated guide bars secured at one end thereof to said outer housing and disposed parallel with said clamping means between oppositely laterally projecting, outwardly diverging pairs of said blades; and a link pivoted at one end of each said blade adjacent to the outer end of the blade, the links of each said pair of blades having the inner ends thereof pivoted to each other and slidably engaging an elongated, longitudinally directed slot in the adjacent guide bar whereby the pivoting of one blade of a pair in a horizontal direction causes opposite pivotal movement of like extent in the other blade of said pair.
 10. In a machine for forming sheet metal ductwork as set forth in claim 9: said frame including horizontal guideways extending perpendicular to said clamping means and table in a fore and aft direction; means mounting said support for sliding movement of said cylinder and piston motor on said guideways; means for moving said support along said guideways; means holding the outer end of that blade of each pair which is disposed adjacent to said clamping means whereby movement of said support and cylinder and piston motor in the aft direction away from said clamping means causes said pairs of blades to spread apart symmetrically to widen the X-shaped crown and whereby opposite movement of said support and cylinder and piston motor causes said pairs of blades to symmetrically close to narrow the X-shaped crown.
 11. In a machine for forming sheet metal ductwork as set forth in claim 1: die means provided adjacent to at least one lateral side of said table and on said frame forming a cleat connector flange at said one side edge of the second wall when said table is pivoted to said perpendicular position; said die means comprising an inner flange forming portion in the form of a flat, relatively thin member projecting laterally from one end of said table and having a straight outer edge perpendicular to said clamping means; an outer flange forming portion carried by said frame and comprising a bar member so positioned that when said table is folded upwardly, the edge of said inner flange forming portion is disposed closely adjacent to an edge of said bar member, a portion of the blank projecting outwardly beyond the edge of said inner flange forming portion whereby it is bent forwardly at right angles upon contact with said edge of said bar member; means for mounting said outer flange forming portion for reciprocating movement parallel with said clamping means whereby said bar member can be moved inwardly in overlapping relationship with said inner flange forming portion to bend the edge of the blank at one end of said second wall to complete a cleat connector flange; means for mounting said inner flange forming portion for reciprocating movement parallel with the movement of said outer flange forming portion whereby both said portions can be retracted to disengage them from the cleat connector flange and allow the table to pivot downwardly.
 12. In a machine for forming sheet metal ductwork as set forth in claim 11: said outer flange forming portion being so shaped as to provide a triangular plane having its base at the bottom of said bar member and converging upwardly to the top of said bar member, said plane being angled forwardly and laterally outwardly with respect to the inner flange forming portion whereby the outwardly extending portion of the blank which projects laterally beyond the inner flange forming portion first strikes the broad base of the plane as it pivots upwardly and is progressively formed by said plane and the edge of said bar member to a position at right angles with the main portion of the second wall.
 13. In a machine for forming sheet metal ductwork as set forth in claim 12: said means mounting said outer flange forming portion for reciprocating movement comprising a slide member; power means for reciprocating said slide member; means pivotally mounting said bar member to one end of said slide member for pivoting about a vertical axis disposed adjacent to the inner end of said slide member; and resilient means strongly urging said bar member into alignment with said slide member and allowing said bar member to pivot outwardly a slight amount as it slides over the inner flange forming portion to form the cleat.
 14. In a machine for forming sheet metal ductwork as set forth in claim 13: said machine having said die means provided adjacent to both lateral sides of said table, both die means acting laterally inwardly to form inwardly turned cleat connector flanges at both side edges of the second wall.
 15. In a machine for forming sheet metal ductwork as set forth in claim 1: stop means carried at the outer edge of said pivoted table portion and projecting thereabove, against which the forward edge of the blank abuts to properly position the blank in the fore and aft direction prior to said clamping means clamping the sheet metal blank to said bed.
 16. In a machine for forming sheet metal ductwork as set forth in claim 15: said stop means comprising at least two stop members disposed in spaced relationship upon the forward edge of said table; each said stop member being elongated and disposed substantially vertically against the forward edge of said table, the upper portion of said stop member projecting downwardly a substantial distance below said table; bracket means carried by said table and pivotally mounting each said stop member at a medial portion thereof below the level of said table; and means adapted to hold the upper end portion of each said stop member against the forward edge of said table for initial positioning of the blank and during the upward pivoting movement of said table and for pivoting the upper end of said stop member away from the table edge and away from the blank when said table is in its upper position whereby to release the edge of said blank before the table is lowered back to its level position.
 17. In a machine for forming sheet metal ductwork as set forth in claim 16: said means for holding and pivoting said stop members each comprising a rod disposed below said bracket means and oriented in the fore and aft direction, the forward end of said rod being pivotally connected to said stop member below the pivot of said bracket means; apertured guide means slidably receiving said rod rearwardly of the pivoted end of said rod; means biasing the lowermost end portion of said stop member in a rearward direction whereby the upwardly projecting end portion of said stop member is biased away from the forward edge of said table; a cam member abutting the rearwardly directed end of said rod and pressing said rod forwardly whereby the upper end portion of said stop member is held adjacent to the forward edge of said table; said cam member having a cam surface portion allowing said rod to move rearwardly whereby the upper end portion of said stop member is allowed to pivot forwardly away from the forward edge of said table; and power means for moving said cam whereby said surface portion abuts the end of the rod after the table has been pivoted to its uppermost position.
 18. In a machine for forming sheet metal ductwork as set forth in claim 1: said table having stop means against which a forward edge of the blank abuts to initially position the blank in a forward direction; offset strap lock forming die means mounted on said frame adjacent to one lateral edge of said bed and having fixed and vertically movable jaws between which a side edge portion of the blank rearwardly of said clamping means is disposed; said strap lock forming die means having stop means associated therewith for positioning the adjacent side edge of the blank prior to punching offset strap locks therein; and power means for actuating said strap lock forming die means.
 19. In a machine for forming sheet metal ductwork as set forth in claim 18: means mounting said strap lock forming dies comprising a fore and aft disposed shaft carried by said frame; and clamp means for adjustably positioning each said strap lock forming die along said shaft.
 20. In a machine for forming modular portions of ductwork from sheet metal blanks, a supporting frame having a flat bed; means providing a tough, elastic surface on said bed; said frame having a table portion pivoted at its inner edge and disposed coplanar with and extending from said bed in a lowered position and pivotable to a position perpendicular to said bed; an elongated clamping bar for clamping the blank to said bed along a line parallel with and closely adjacent to said inner edge of said table whereby upward pivoting of said table bends the blank about said clamp to an L-shape and forms two right angularly disposed, substantially rectangular walls, one of the walls overlying said bed; a pair of inner flange forming die members mounted at the side edges of said table perpendicular to the axis of said table; a pair of outer flange forming die members carried by said frame and affording shaping means against which portions of said blank projecting laterally beyond said inner flange forming die members at the side edges of said table are pressed and bent to right angles when said table is pivoted upwardly; said outer flange forming die members being movable laterally inwardly over said inner flange forming die members to complete backwardly turned cleat connector flanges; said inner flange forming die members being retractable whereby they are disengaged from said connector flanges to allow said table to return to the horizontal position; a press forming device carried by said frame above the one wall of the blank, said device being movable downwardly for impressing a slight, frustopyramidal crown in the one wall; said modular portion adapted to be assembled with a like modular portion to provide a section of rectangular ductwork having two parallel, opposite crowned walls and two parallel, opposite plain walls.
 21. In a machine for forming modular portions as set forth in claim 20: stop means carried at the outer, forward edge of said table portion and projecting thereabove, the forward edge of the blank abutting said stop to properly position the blank in the fore and aft direction prior to clamping the blank to said bed.
 22. In a machine for forming modular portions as set forth in claim 21: said stop means comprising at least two stop members disposed in spaced relationship upon the forward edge of said table; each said stop member being elongated and disposed substantially vertically against the forward edge of said table, a lower portion of each stop member projecting downwardly a substantial distance below said table; bracket means carried by said table and pivotally mounting said stop member at a medial portion thereof below the level of said table; and means adapted to hold the upper end portion of said stop member against the forward edge of said table for initial positioning of the blank and during the upward pivoting movement of said table and for pivoting the upper end of said stop member away from the table edge and away from the blank when said table is in its upper position whereby to release the edge of said blank before the table is lowered back to its level position.
 23. In a machine for forming modular portions as set forth in claim 22: said means for holding and pivoting each said stop member comprising a bracket carried by said table means, said bracket providing a pivoted connection for a medial portion of said stop member below the level of said table; a rod disposed below said bracket and oriented in the fore and aft direction, the forward end of said rod being pivotally connected to said stop member below the pivot of said bracket; apertured guide means slidably receiving said rod rearwardly of the pivoted end of said rod; means biasing the lowermost end portion of said stop member in a rearward direction whereby the upwardly projecting end portion of said stop member is biased away from the forward edge of said table; means for retracting said inner flange forming die members, each including cam means abutting the rearwardly directed end of one rod of one of said stop means and pressing said rod forwardly whereby the upper end portion of the associated stop member is held adjacent to the forward edge of said table; each said cam member having a cam surface portion allowing the associated rod to move rearwardly when the inner flange forming die members are retracted whereby the upper end portion of each said stop member is allowed to pivot away from the forward edge of the table at the same time that the inner flange forming die members are disengaged from the cleat connector flanges.
 24. In a machine for forming modular portions as set forth in claim 20: said press forming device comprising a cylinder and piston motor mounted on a support a substantial distance above said flat bed; a tubular noncircular housing secured at one end to said support coaxial with said motor and depending from said support; said motor having a piston rod extending downwardly through said housing and projecting below the lower end of said housing; an outer noncircular housing of shorter axial dimension than said first mentioned housing slidably telescoped over said first mentioned housing, said housings being nonrotatable with respect to each other; means securing the lower end of said piston rod to said outer housing; means mounting inner ends of four crease forming blades to said outer housing, said blades being symmetrically arranged to impress a substantially X-shaped crown in the one wall of the blank.
 25. In a machine for forming modular portions as set forth in claim 24: said means mounting the inner ends of said blades comprising axially vertical bearing means mounting said blades for horizontal pivotal movement, there being sufficient play in said bearings to afford slight up and down movement of the outer ends of said blades; a longitudinally adjustable rod connecting the outer end portion of each said blade with an upper portion of said outer housing whereby said rods extend outwardly and angle downwardly and afford means for adjusting the relative pressure on the blank between the inner and outer ends of said blades when said motor is actuated.
 26. In a machine for forming modular portions as set forth in claim 25: a pair of horizontally disposed, oppositely projecting, elongated guide bArs each secured at one end thereof to said outer housing and disposed parallel with said clamping bar between oppositely laterally projecting, outwardly diverging pairs of said blades; and a link pivoted at one end to each said blade adjacent to the outer end of the blade, the links of each said pair of blades having the inner ends thereof pivoted to each other and slidably engaging an elongated, longitudinally, directed slot in the adjacent guide bar whereby the pivoting of one blade of a pair in a horizontal direction causes opposite pivotal movement of like extent in the other blade of said pair.
 27. In a machine for forming modular portions as set forth in claim 26: said frame including horizontal guideways extending perpendicular to said clamping means and table in a fore and aft direction; means mounting said support for sliding movement of said cylinder and piston motor on said guideways; means for moving said support along said guideways; means holding the outer end of that blade of each pair which is disposed adjacent to said clamping means whereby movement of said support and cylinder and piston motor in the aft direction away from said clamping means causes said pairs of blades to spread apart symmetrically to widen the X-shaped crown and whereby opposite movement of said support and cylinder and piston motor causes said pairs of blades to symmetrically close to narrow the X-shaped crown.
 28. A cross break device for impressing a slightly frustopyramidal crown in a wall of sheet metal ductwork during the forming thereof, said cross break device mounted upon a frame having a flat bed; means providing a tough elastic surface on said flat bed; said cross break device comprising a cylinder and piston motor mounted on a support a substantial distance above said flat bed; a tubular noncircular housing secured at one end to said support coaxial with said motor and depending from said support; said motor having a piston rod extending downwardly through said housing and projecting below the lower end of said housing; an outer noncircular housing of shorter axial dimension than said first mentioned housing slidably telescoped over said first mentioned housing, said housings being nonrotatable with respect to each other; means securing the lower end of said piston rod to said outer housing; means mounting inner ends of four crease forming blades to said outer housing, said blades being symmetrically arranged to impress a substantially X-shaped crown in the sheet metal.
 29. In a cross break device as set forth in claim 28: said means mounting the inner ends of said blades comprising axially vertical bearing means mounting said blades for horizontal pivotal movement, there being sufficient play in said bearing means to afford slight up and down movement of the outer ends of said blades; a longitudinally adjustable rod connecting the outer end portion of each said blade with an upper portion of said outer housing whereby said rods extend outwardly and angle downwardly and afford means for adjusting the relative pressure on the sheet metal between the inner and outer ends of said blade when said motor is actuated.
 30. In a cross break device as set forth in claim 29: a pair of horizontally disposed, oppositely projecting, elongated guide bars secured at one end thereof to said outer housing and disposed between oppositely laterally projecting, outwardly diverging pairs of said blades; and a link pivoted at one end to each said blade adjacent to the outer end of the blade, the links of each said pair of blades having the inner ends thereof pivoted to each other and slidably engaging an elongated, longitudinally directed slot in the adjacent guide bar whereby the pivoting of one blade of a pair in a horizontal direction causes opposite pivotal movement of like extent in the other blade of said pair.
 31. In a cross break device as set forth in claim 30: said frame including horizontal guideways extending perpendicular to said table in a fore and aft direction; means Mounting said support for sliding movement of said cylinder and piston motor on said guideways; means for moving said support along said guideways; means for holding the outer end of one blade of each pair disposed on the same side of said cross break device whereby movement of said support and cylinder and piston motor in the direction of said guideways away from said holding means causes said pairs of blades to spread apart symmetrically to widen the X-shaped crown and whereby opposite movement of said support and cylinder and piston motor causes said pairs of blades to symmetrically close to narrow the X-shaped crown.
 32. In a machine for forming sheet metal ductwork wherein the machine has a frame, a horizontal bed, clamping means adjacent to one edge for clamping a sheet metal blank, and a pivoted table disposed adjacent to the one edge coplanar with the bed when in a lowered position and pivotable upwardly to form a right angularly disposed wall; die means for forming cleat connector flanges at the vertical side edges of the wall comprising inner flange forming portions in the form of flat, relatively thin members projecting laterally from the ends of the table and having straight outer edges; outer flange forming portions carried by said frame and comprising bar members so positioned that when said table is folded upwardly, the edges of said inner flange forming portions are disposed closely adjacent to the edges of said bar members, a portion of the blank projecting outwardly beyond the edges of said inner flange forming portions and being bent forwardly at right angles upon contact with said edges of said bar members; means for mounting each said outer flange forming portion for reciprocating movement parallel with said clamping means whereby said bar members can be moved inwardly in overlapping relationship with said inner flange forming portions to bend the lateral edges of the blank to complete the cleat connector flanges; means for mounting said inner flange forming portion for reciprocating movement parallel with the movement of said outer flange forming portions whereby both said portions can be retracted to disengage them from the cleat connector flanges and allow the table to pivot downwardly.
 33. In a machine as set forth in claim 32: each said outer flange forming portion being so shaped as to provide a triangular plane having its base at the bottom of the bar member and converging upwardly to the top of said bar member, said plane being angled forwardly and laterally outwardly with respect to the inner flange forming portion whereby the outwardly extending portion of the blank which projects laterally beyond the inner flange forming portion first strikes the broad base of the plane as it pivots upwardly and is progressively formed by said plane and the edge of said bar member to a position at right angles with the main portion of the wall.
 34. In a machine as set forth in claim 32: said means mounting said outer flange forming portion for reciprocating movement comprising a slide member; power means for reciprocating said slide member; means pivotally mounting said bar member to one end of said slide member for pivoting about a vertical axis disposed adjacent to the inner end of said slide member; and resilient means strongly urging said bar member into alignment with said slide member and allowing said bar member to pivot outwardly a slight amount as it slides over the inner flange forming portion to form the cleat.
 35. In a machine as set forth in claim 32: stop means carried at the outer edges of said pivoted table portion and projecting thereabove for positioning a forward edge of the blank of sheet metal; said stop means comprising at least two stop members disposed in spaced relationship upon the outer edge of said table; each said stop member being elongated and disposed substantially vertically against the forward edge of said table; a lower portion thereof projecting downwardly a substantial distance below said table; bracket meanS carried by said table and pivotally mounting said stop member at a medial portion thereof below the level of said table; a rod disposed below said bracket means and oriented perpendicular to the outer edge of said table, the outer end of said rod being pivotally connected to said stop member below the pivot of said bracket means; apertured guide means slidably receiving said rod spaced inwardly of the said outer edge of said table; means biasing the lowermost end portion of said stop member inwardly whereby the upwardly projecting end portion of said stop member is biased away from the forward edge of said table; said means for mounting said inner flange forming portion including a cam abutting the inwardly directed end of said rod and pressing said rod forwardly whereby the upper end portion of each said stop member is held adjacent to the forward edge of said table; said cam member having a cam surface portion allowing said rod to move inwardly whereby the upper end portion of said stop member is allowed to pivot away from the forward edge of said table; said cam surface portion being moved into alignment with said rod when said inner flange forming portions are retracted thereby freeing the edge of the sheet metal.
 36. In a machine for forming modular portions of sheet metal ductwork from a sheet metal blank, a frame; said frame having a flat bed; means providing a resilient surface on said bed; a vertically movable, elongated clamping bar disposed above said bed adjacent to and parallel with one edge thereof; power means for actuating said clamping bar; a pivoted table mounted on said frame adjacent to said one edge and pivotable upwardly from a horizontal to a vertical position whereby to bend a sheet metal blank held at a midportion thereof by said clamping bar to form horizontal and vertical walls; power means for actuating said table; a vertically acting press forming device mounted above said bed for impressing a slight crown in the horizontal wall; power means for actuating said press forming device; a pair of inner flange forming die members carried by, and comprising straight lateral side edges of, said table; outer flange forming die members carried by said frame and having straight edges disposed closely adjacent to said side edges of said inner flange forming die members when said table is raised, the blank projecting laterally beyond said table and being pressed against said outer die members and bent at right angles when said table is pivoted to the vertical position; power means for reciprocating said outer die members whereby they can be moved inwardly over said inner die members to complete backwardly turned cleat connector flanges at the lateral edges of said vertical wall; power means for reciprocating said inner die members for disengagement from the cleat connector flanges; a pair of stop bars pivotally mounted adjacent to the outer nonpivoted edge of said table for positioning a forward edge of the blank, portions of each bar projecting above and below said table; cam and cam follower means associated with said stop bars and said power means of said inner die members whereby said inner die members are retracted for disengagement from the cleat connector flanges concurrently with pivoting of said stop bars away from said outer table edge to clear the edge of the vertical wall; and electrical control means causing said clamping bar to clamp the blank to said bed, said press forming device to lower and impress the horizontal wall, said table to pivot upwardly to form the vertical wall and bend the lateral edge portions thereof at right angles, said outer die members to extend and complete the cleat connector flanges, both said inner and outer die members to retract and said stop bars to pivot away from said outer edge of said table, said table to return to a horizontal position, and said clamping bar and press forming device to raise, in an automatic series of sequential and concurrent operations.
 37. In a machine as set forth in claim 36: said control means including a single relay means for causing said clamping bar and press forming device to lower; and means responsive only to the lowering of said press forming device for causing said table to pivot upwardly whereby said table is not actuated until after the blank is firmly gripped by said clamping bar and press forming device.
 38. In a machine as set forth in claim 37: said control means including means responsive only to said table being pivoted upwardly causing said outer die members to move inwardly to complete the cleat connector flanges.
 39. In a machine as set forth in claim 38: said control means including means responsive to said outer die members moving inwardly causing said inner die members to retract and said stop bars to pivot away from the forward edge of the blank and said outer edge of said table.
 40. In a machine as set forth in claim 39: said control means including means responsive to said inner die members retracting causing said outer die members to retract, said table to return to a horizontal position, and said clamping bar and press forming device to rise; said control means including means delaying the return of said inner die members to the extended position until said table has pivoted downwardly at least partway to assure that said inner die members and stop bars clear the cleat connector flanges and upper edge of the vertical wall. 